A surface texture measuring instrument may be used for measuring the surface roughness of a measurement work, such as the surface rising and falling, the contour, or other features of the measurement work. The surface texture measuring instrument may include a detector that supports, to be displaceable, a stylus having a sensing pin at the tip end to be touched on the surface of the measurement work, and a drive unit that moves the detector in a measurement direction.
With such a surface texture measuring instrument, the sensing pin of the detector is touched onto the measurement surface of the measurement work. In this state, when the detector is moved in the measurement direction by the drive unit, some displacement is observed to the sensing pin depending on the rising and falling of the measurement surface of the measurement work. The resulting displacement of the sensing pin is used as a basis to measure the surface roughness, the surface rising and falling, or others of the measurement work.
Due to such measurement principles, to measure the surface texture such as the surface roughness of the measurement work with high accuracy, there needs to highly accurately keep the drive unit straight with the reason that the detector is moved linearly in the measurement direction. The problem here is that the straightness accuracy of the drive unit exerts an influence on the measurement operation due to the limitations of the drive unit in view of processing and assembly accuracy.
To solve such a problem, JP-A-11-118473 proposed a data processor of a surface roughness and contour measuring instrument. The surface roughness and contour measuring instrument is provided with a pickup that detects any displacement observed to a sensing pin to be touched on the measurement surface of a measurement work, and a drive mechanism that moves the pickup. In the instrument, at shipment or others, the straightness accuracy of the drive mechanism is stored in advance in storage means as correction data through measurement of an optical flat. At the actual measurement, the correction data stored in the storage means is subtracted from the measurement data so that any deviation component in view of the straightness accuracy of the drive mechanism is eliminated from the measurement data.